All this visible universe is not unique
in nature, and we must believe that there are, in other regions of space,
other worlds, other beings and other men. Lucretius (99 - 55 B.C.)

A glider pilot flying at 6000' south of Dalby, Queensland, in
1997 saw below him an unusual aircraft which he attempted to contact on
area frequency without success. He described it as being somewhat diamond
shaped viewed from above, and not unlike a stealth bomber, but opaque white.
Flight Services said there were no military aircraft in the area. (The
well-respected pilot asked to remain anonymous. He is not the type to imagine
such things)

Several experienced glider pilots flying out of Lake Keepit in NSW each
independently saw something streak across the sky sometime in the early
1990's. One of those who saw it is a doctor and another is a Chief Flying
Instructor.

Francis Chichester mentions in The Lonely Sea and the Sky (Hodder
& Stoughton 1964, page 165) something odd he saw whilst on his pioneer
solo flight from New Zealand to Australia in a Gypsy Moth seaplane.

"Suddenly, ahead and thirty degrees
to the left, there were bright flashes in several places, like the dazzle
of a heliograph. I saw a dull grey-white airship coming towards me. It
seemed impossible, but I could have sworn that it was an airship,
nosing towards me like an oblong pearl ..." More

There are of course many hundreds of other recorded instances, but those
above are not well known.